Abundant Housing LA estimates that Los Angeles County has a shortfall of over 700,000 homes that are affordable to households earning less than 80% of the area median income ($73,000). This is based on an estimated total housing need of 2.7 million homes across all income levels throughout Southern California. This is also in line with the California Housing Partnership’s recent estimate that Los Angeles County has a shortfall of 500,000 homes that are affordable to households earning less than 50% of the area median income.
Assuming an average per-unit cost of $420,000, it would cost nearly $300 billion to construct 700,000 units of affordable housing, or $37 billion per year throughout the upcoming 8-year Regional Housing Needs Assessment (RHNA) cycle. If local, state, and federal governments were to fund 20% of the capital costs, relying on nonprofit and private capital for the remaining 80%, the cost to governments would be $60 billion, or $7.5 billion per year.
This spreadsheet contains additional detail and sourcing for this estimate.